Resnatron filament basket



Nov. 2, 1954 w. H. KOHL 2,693,544

RESNATRON FILAMENT BASKET Filed Dec. 14, 1951 Z5 I 28 *2? 24 -13 17 J u U Fr 11/ I I [a INVENTOR.

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United States Patent Ofifice 2,693,544 Patented Nov. 2, 1954 RESNATRON FILAMENT BASKET Walter H. Kohl, Cedar Rapids, Iowa, assignor to Collins Radio Company, Cedar Rapids, Iowa, a corporation of Iowa Application December 14, 1951, Serial No. 261,649

3 Claims. (Cl. 313-273) This invention relates in general to resnatron filament baskets and in particular to a basket which is free to expand at elevated temperatures without physical distortion.

As high powered resatron tubes have been experimented with more and more it has become obvious that the cathode, generally referred to as a basket, is a very important element. Great care must be taken to assure that the basket is symmetrically placed within the resnatron and that no physical distortion caused by temperature changes upsets the initial alignment.

It is an object of this invention therefore to provide an improved resnatron filament basket which provides constant alignment during temperature changes.

Another object of this invention is to provide a resnatron filament basket which produces a copious flow of electrons from the long active portion of the filament.

Yet another object of this invention is to provide an easily constructed resnatron filament basket.

Further features, objects and advantages of this invention will become apparent from the following description and claims when read in view of the drawings in which;

Figure 1 is a top view of a resnatron filament basket according to this invention;

Figure 2 is a sectional view taken on line 22 of Figure 1;

Figure 3 is a top view of a modification of the invention; and,

Fggure 4 is a sectional view taken on line 4-4 of Figure The resnatron filament basket shown in section in Figure 2 is mounted between a top supporting member, designated generally as 10, and a lower supporting member designated generally as 11. A plurality of filament elements 12 are generally race track in shape but have breaks adjacent one end thereof so that they do not form a closed circuit. The filaments 12 might be made of tungsten, for example. The upper and lower supporting'members and 11 might be made of copper which is water cooled by suitable tubing in a well known manner.

Attached to the lower end of the upper supporting member 10 is a ring 13. The ends 14 of the filament elements 12 abut against the ring 13 and are attached to form a unitary assembly by a ring of filler metal 16 which is received in an annular groove 17 formed in the lower end of the member 10.

A second ring 18 is mounted to the upper end of the lower supporting member 11, and clamps the other ends 19 of the first elements 12. The member 18 is also formed with an annular groove 21 into which is received a ring 22 of filler metal.

To assemble the basket the unit is held by a suitable jig in the relationship shown in Figure 2 and is placed into a furnace with a temperature high enough to melt the filler metal so that it flows to join the ends of the filaments to the various holding pieces by well known brazing techniques. After cooling the completed basket is removed from the holding jig. The iig may be of the type described in my copending application entitled Assembly for Resnatron Filament Serial No. 128,380. filed November 19, 1949.

Figure 1 is a top view of the filament basket shown in Figure 2.

A modification of the invention is shown in Figures 3 and 4 wherein the upper holding piece 10 and the lower holding piece 11 support a filament structure comprising an internal cylinder 23 which has its lower end 24 clamped and brazed between the ring 13 and the upper support 10 and which has its upper end 26 attached or bent over to form an outer cylinder, designated generally as 27. The outer cylinder 27 has a lower portion 28 that is clamped and brazed between ring 18 and member 11.

The outer cylinder 27 is formed with a plurality of openings 29 that extend axially thereof so as to form emitting portions 31. The inner and outer cylinders may be formed of tantalum or the inner cylinder may be made of tantalum and the outer cylinder of tungsten.

In both modifications an electrical potential is applied between the upper holding member 10 and the lower holding member 11. Since these members are separated from each other the current must flow through the filament structures, and the active portions 12 in the modification shown in Figure 2. Because the resistivity of these portions is substantially higher than the upper and lower holding portions and the cross sectional area is small, they are raised to an electron emission temperature. The resulting increase in temperature causes thermal expansion but because of the configuration of the filament elements the expansion will be substantially compensated.

For example, the rear portions, designated as 32 in Figure 2 will expand upwardly from the ends 14, and the outer portions 12 will expand upwardly from the ends 19. Since the portions are of the same order of magnitude in size the thermal expansion will be substantally compensated. A relatively long hot portion will be obtained since the heating current flows through the portions 32 as well as the portions 12. Thus, there will be very little end-cooling of the upper ends of the portions 12.

The modification of Figure 4 obtains substantially the same advantages except that it also provides a shield for the upper supporting member 10. The cylinder 23 will become quite hot from the heating current because its cross sectional area is of the same order of magnitude as the total cross sectional area of the elements 31. This is true because the cylinder 23 is smaller in diameter than the cylinder 27 and is formed with no openings.

It is also possible in the modification shown inFigure 4 to use an internal cylinder made of tantalum and an external cylinder made of tungsten so as to compensate for any variations in thermal expansion. These materials have different coeflicients of thermal expansion and the desired compensation may be made.

Although this invention has been described with respect to particular embodiments thereof, it is not to be so limited as changes and modifications may be made therein which are within the full intended scope of the invention as defined by the appended claims.

I claim:

1. A resnatron filament basket comprising, a top supporting member, a lower supporting member, an internal cylinder connected to the top supporting member and extending upwardly therefrom, an external cylinder connected to the lower supporting member and extending upwardly therefrom, the top portions of said internal and external cylinders joined to ether, and a plurality of slots formed in the external cylinder to form a number of electron emitting portions.

2. A resnatron filament basket comprising, a top supporting member,-a bottom supporting member, an internal cylinder connected to the top supporting member and extending upwardly therefrom. an external cylinder connected to the bottom supporting member and extending upwardly therefrom concentric about the internal cylinder, the upper ends of said internal and external cylinders connected together, and a plurality of slots formed in the external cylinder to produce a number of electron emitting portions.

3. A resnatron filament basket comprising, a top supporting member, a lower supporting member, said top supporting member and said lower supporting member mounted in axial alignment and terminating closely adjacent each other, a plurality of electron emitting filamerit elements mounted between the top supporting member and the lower supporting member, each of said filament elements comprising strips having two parallel straight portions joined at one end, said straight portions comprising active electron emitting" members; the other end of the first straight portion attached to the top supporting member and the other end of the second straight portionattached to: the lower: supporting member; and the lengths of. the active electron emittingmembers.- being. substantiallyv greater than the distance betweenthe top: and lower. supporting members,

References Cited in the file of this patent Number UNITED STATES PATENTS Name Date Swan Oct. 19, 1880 Mutscheller July 10, 1934 Mourorntseif et a1 May 19, 1942 ONeill Nov. 2, 1948 Butler May 3, 1949 Kohl June 3, 1952 Kohl Nov. 11, 1952 

